The present invention relates to mineral mining installations which employ water spray nozzles and more particularly to apparatus for controlling the operation of such nozzles.
It is well known to utilize water spraying nozzles in mineral mines which primarily serve to suppress dust. Usually the nozzles are directed to spray water towards the mineral, e.g. coal, face and the nozzles are selectively operated by the movement of a mineral mining machine, e.g. coal plough, in such a way that only the nozzles in the immediate vicinity of the machine during its travel are actually operated. For such a purpose a magnetic device has been provided on the machine to actuate magnetically-sensitive control valves associated with the nozzles. However, in practice apparatus of this kind is apt to be unreliable and the magnetic device does not always cause the valves to operate at the same distance. In any event it is difficult to construct the apparatus with the necessary precision and in the harsh working conditions encountered in a mine working the apparatus is prone to damage and breakdown. It is also known to provide each control valve with a mechanically operated lever which is moved directly by the impact of the machine as the latter progresses along the appropriate section of the working. Again although such apparatus can be more robust it is also prone to damage and in any event suffers a high degree of wear. Another disadvantage of this mechanical apparatus is that each control valve can usually only adopt its open position permitting water spraying from its associated nozzles when the lever is actually in contact with the machine. This period is not really long enough to efficiently promote dust suppression and to overcome this problem retardation means which inhibits the closure of the valve until a pre-determined time has elapsed after the passage of the machine has been provided. This measure has not been wholly successful however and considerably increases the cost and complexity of the apparatus.
With regard to the foregoing a general object of the present invention is to provide an improved form of control apparatus.